The aim of this proposal is to develop a small caliber cholangioscope that is torquable when passed through a standard duodenoscope to allow improved directional control of the cholangioscope within the biliary tree. Current small caliber cholangioscopes offer improved access to the biliary tree in comparison to larger "daughter" cholangioscopes. However, maneuverability of these smaller scopes has been limited. We hypothesize that construction of a new type of small cholangioscope using a flexible steel shaft will provide the ability to torque the scope to assist steering within the biliary tree. Our goal is to construct a flexible and torquable cholangioscope that remains within a suitable size range less than 3.1 mm) to allow passage through a therapeutic duodenoscope and to permit access to the biliary tree beyond the common hepatic duct bifurcation. The scope will have, in addition to torquability, a cable guided steering mechanism. The combination of its small caliber, torque-controlled steering and cable-guided steering will allow predictable access to second and possibly third level bile duct branches for inspection, biopsy and passage of guidewires or additional therapeutic instrumentation. PROPOSED COMMERCIAL APPLICATIONS: The total US market for endoscopes is approximately $30 million with small (less than 3 mm) scopes accounting for less than 1% of that market. With increased maneuverability to access the biliary tree and to provide direct biopsy, diagnosis of PSC using cholangioscopes will increase the demand for this product. Additional markets which will open up with the development of a more controllable miniature scope include arthroscopy of small joints.